Rock Tumbling pebbles from a Devon Beach. Success and failure!

I found this bag of rocks under the seat of my car, they had been there for over a year! I picked them up on a Devon beach on the south coast of England. One of the rocks was a bit special, and rock tumbling the lot was as always great fun and at the same time just a bit frustrating. Most of the stones polished brilliantly but a few were a disappointing failure. Ho hum!